1. Field of the Invention
The present invention relates generally to a method and apparatus for defining and displaying extracted images in windowing environments, and more particularly for defining and displaying non-rectangular bitmaps in a display device context using a rectangular bitmap.
2. Description of the Prior Art
A bitmap is a pixel-by-pixel definition of an image, and is used to express the information needed to display an image. Typically, the bitmap provides a designation of the display state for each pixel of the image. For a monochrome display, this merely involves specifying whether each pixel is turned on or off. For a color display, however, a display color must be specified for each pixel. There are many applications for imaging a bitmap on a display device. For example, bitmaps can be used to define one or more icons in a windowing environment, such as, for example, Microsoft Windows.RTM.. As the applications for windowing environments become more sophisticated, there is an increasing demand to express information in a very easy-to-understand manner. Icons are well-suited to graphically express information in such a manner.
Often images, such as icons, are nonrectangular, or irregular, in shape so as to accurately represent an image and easily convey an associated function to the user. However, bitmaps are conventionally specified as rectangular regions in most bitmap files, e.g., ".BMP" or ".PCX" files which are industry standard formats for bitmap files. Therefore, the pixels of a rectangular region which are not part of the image must be set to the same color as the window background so that the image will stand out clearly.
However, the window background color may be altered, as commonly occurs in windowing environments. In that situation, if the rectangular structure of the bitmap is not altered, the displayed image will look "dirty" because the portion of the rectangular bitmap surrounding the irregular image will have a different color than the color of the window background. Therefore, before an irregular bitmap image, such as, for example, an icon, is displayed, it is preferable to alter the rectangular structure of the stored bitmap.
The subject invention is directed to a novel and unique method and apparatus for defining an irregular bitmap in a rectangular bitmap structure and for displaying the irregular bitmap on a display screen in windowing environments. The subject invention also has broader applications for extracting one or more images defined within a bitmap.